OFFICIAL estimates of the economic benefits of the controversial HS2 high speed rail network were rolled back on Tuesday, on the same day Plaid Cymru pledged to vote against the multi-billion pound scheme unless the Welsh Government receives a proportion of the funding.

The UK Government now only expects that every £1 spent will generate £2.30 – not the £2.50 estimated last year.

Its “strategic case” for the rail project, published on Tuesday, suggests North Wales could benefit from faster journeys to Birmingham and London via Crewe.

The report also drew on one published by Network Rail and engineering company Atkins which said there would be 14 years of weekend engineering work on the railways if HS2 did not go ahead.

However, Plaid Cymru Dwyfor Meirionnydd MP Elfyn Llwyd insisted the £42.6bn project was for the benefit of England and as such the Welsh Government should receive a share of funding under the Barnett formula. He estimated this could be the range of £2.3bn to £5bn.

Mr Llwyd said: “It appears to be a vanity project; I do not think it’s going to benefit any part of Wales greatly, and at that kind of cost it’s a huge amount of outlay and therefore our view is firm: unless they can sign-up to say we will get a full Barnett consequential equivalent on every year of HS2 expenditure [then] we will not vote for HS2.”

A Department for Transport spokesman stressed HS2 would benefit the “whole of the UK,” saying: “It doesn’t go to Wales but clearly it will free up capacity on the existing rail network.”

He added that as the HS2 network will be integrated with conventional lines many journeys will be speeded up and Welsh contractors had the opportunity to win business during the construction process.

Conservative Shadow Assembly transport minister Byron Davies said: “HS2 will create 50,000 jobs a year during construction, boost the British economy by up to £15bn a year and when completed will improve journey connectivity from North Wales.”

Alison Munro, chief executive of HS2 Ltd, said the boost to the economy would be for the good of the whole country.